Fix early call to smartparens in ruby

[bmag]

sp-with-modes was called before smartparens was loaded, so I wrapped it in a with-eval-after-load. I wasn't sure if this needs to go in a ruby/post-init-smartparens instead, or if smartparens should be replaced with smartparens-config as the argument to with-eval-after-load.

I don't use Ruby, so I couldn't test it. Can some Ruby user give it a try please? Should also check that the pre and post handlers definition in a Ruby file match the configuration here and are not overridden by smartparens-config.

This should fix one of the two issues encountered in #4098 - the Symbol's function definition is void: sp-with-modes error.

[syl20bnr]

Thank you!
I simplified the configuration using a post-init function in commit f20dfec
Cherry-picked in develop branch, you can safely delete your branch.